In the aforementioned application (see also the corresponding German Patent Application P 35 14 041), there is described a measuring device for the width of the pressing zone and/or the pressing surface area of a roller, especially a feed roller, on a roll of material wound from a web of sheet material, e.g. paper.
In this measuring device, radiation sources are located in the surface of the roller whose radiation is directed toward the roll of material and a radiation detector is located to detect the radiation reflected from the roll of material.
The pressing zone width and/or the pressing surface area of the roll of material is determined with a computer or signal analyzer from the interruption of the output from the radiation detector during the covering of the radiation source by the roll of material and a signal fed from a sheet speed measuring device. The computer can also consider additional parameters determining the roll hardness in calculating the correction factor for the winding operation, including the radius of the roll of material, the roll weight, the length of the roll, the sheet material specific weight (weight per unit area) and the geometry of the winding device.